1. Field of the Invention
The present invention relates to a pulse width processing circuit and, more particularly, to such a circuit for providing an output pulse with a precisely controlled width.
2. Description of the Prior Art
Pulse width processing circuits provide timing pulses for television receivers or video tape recorders (VTR's). Such processing circuits can accept pulses, like the horizontal synchronizing pulses in a composite video signal, and provide more precise timing pulses in response. Processing circuits are used to provide timing pulses, instead of using the horizontal synchronizing pulses directly, because the width of the synchronizing pulses is often not precise enough for use by the receiver or VTR. And since composite video signals can contain noise that might be interpreted as a timing pulse by the receiver or VTR, pulse width processing circuits also provide timing pulses only in response to the synchronizing signals and thus prevent the receiver or VTR from reacting to noise. In short, pulse width processing circuits are used to provide precision-width timing pulses for a receiver or VTR in response to horizontal synchronizing pulses in a composite video signal and to prevent any noise in the video signal from being interpreted by the receiver or VTR as a timing pulse.
However, the precision of the width of the timing pulses provided by known prior art processing circuits is limited because of their principle of operation. As is explained in more detail below, prior art circuits rely on the precision to which a small reference voltage can be set and, in practice, a sufficiently precise reference voltage has proved difficult to achieve.